Not Applicable.
1. Field of Invention
The present invention relates to waste treatment systems, and particularly to a process for the treatment of waste from multiple locations.
2. Related Art
In urban areas residential, commercial or industrial wastes are typically treated by municipal wastewater treatment facilities. In rural areas, individual systems for treating wastewater include septic tanks, mound systems, holding tanks, and aerobic systems. Such individual systems have varying degrees of effectiveness.
In these systems, the waste or wastewater is a mixture of water and contaminants. The terms waste, wastewater, wastewater streams and other similar variations are used to denote this high water-content material at various levels of contamination, by various forms of contaminants.
In areas where access to a municipal wastewater treatment plant is not available, but the population is large enough to install a final treatment plant, the standard practice is to build a gathering system along with a small treatment plant. The collection systems in general take two formsxe2x80x94gravity and pressure systems.
A gravity system relies on gravity to move the sewage water to the final treatment plant. To accommodate the sludge associated with sewage waters, the piping must be large enough to prevent clogging and must generally maintain a gradient, often requiring deep line burial. Lift stations are required at selected intervals to maintain a gradient sufficient to move the wastewater and sludge to the final treatment plant. This method is costly to install and the lift stations require continuous monitoring and maintenance.
In areas where there is a large variation in topography or other conditions preclude deep trenching, a pressure system is employed. In a pressure system, the sewage water and sludge is pumped from waste-generating locations into a main feed line that is connected to the final treatment plant. This main line may follow the topography, so that deep burial of the line is not required. Since the system is pressurized, a smaller line may be used than with a gravity system line. To reduce the potential for clogging, grinder pumps or other mechanisms are used to reduce the size of solids in the wastewater prior to inserting the waste into the gathering system. Pressure systems are generally less costly to install than gravity systems since smaller pipes can be used and trenching is not as deep. However, the grinder pumps, which are essentially small lift stations, are more numerous. The grinder pumps require regular maintenance and expense.
A disadvantage of prior art conventional treatment plants is that such treatment plants have a narrow range of loading rates within which they can provide efficient processing of wastes. Such plants are relatively expensive to expand due to space and equipment requirements.
Individual treatment plants may be placed at each waste-generating location together with a mechanism to disperse the treated wastewater. Septic systems utilize a drainfield to complete the treatment process and to disperse the water into the soil. Septic systems are being phased out in most states due to failures of the systems. Septic systems often allow dispersal of untreated wastewater into the water table, creating a health hazard.
To reduce the potential of groundwater contamination, mound systems, which are a variation of septic systems, have been installed. A mound system creates an artificial separation between the drainfield and the watertable allowing time for the wastewater to be treated in the soil prior to reaching groundwater. These systems are costly, unsightly and require a large area to maintain property setbacks and to insure proper treatment and infiltration.
Aerobic treatment systems allow treatment at the waste-generating site. Aerobic systems treat wastewater in a tank supplied with an air source. Discharge of the effluent from aerobic systems may be accomplished by different methods. Due to the potential for pathogens, viruses and other microorganisms remaining in the wastewater, the wastewater may be disinfected for above ground release or injected below ground to prevent human contact. Disinfection methods include chemicals, ozone, ultraviolet radiation, and combinations thereof. The potential for health hazards varies depending on the system, regular monitoring of the systems and proper maintenance of the systems. Such systems can be relatively costly. Discharge of system effluent presents another problem for the owner. In times of high use, the amount of system effluent may exceed the need for water in the aboveground application.
Below ground injection is safer, but can be more costly to install and requires space to adequately infiltrate the wastewater. Many sites do not have the space to support below ground injection. System failures can create health hazards, produce annoying odors and result in costly repairs.
Accordingly, it is a goal of the present invention to provide a wastewater treatment system and process wherein:
The system allows for individual treatment systems, but reduces the space requirement normally associated with individual systems by collecting the discharge to a final treatment location for final treatment.
The collection piping can be downsized to facilitate installation, since no solids can enter the piping system and no biomass buildup can occur.
The final treatment plant can be down sized to specialize in disinfection of the wastewater, with filtration added, if required.
Grinder pumps are not required, thus reducing the cost and maintenance required with most pressure systems.
The final treatment plant can be upgraded to meet new connection requirements easily with little additional space, as disinfection requires a smaller facility footprint and can handle a wider range in volumes of incoming wastewater than a conventional plant.
Initial costs are reduced since the final treatment plant is not required to be sized to meet final projected growth as the disinfection system can be readily expanded.
The low cost of the collection system allows economical initial installation of collection lines with allowance for future expansion requirements.
The system allows a plurality of pump chambers along the collection network, which allows timed dosing to the collection system. The pump chambers can then be used to average flow fluctuations, resulting in a downsized collection system. Pump chambers may be employed at either or both of each generation site or at various stages of the collection system.
The individual pump chambers will require fewer lift stations in the collection system, since each can function as a lift station, and since the pretreated flow is primarily liquid.
There are individual treatment systems, but the system provides a final treatment discharge point for the treated effluent. This allows a single point of monitoring for all systems.
The present invention provides a system and process for treating wastewater generated at multiple locations. The system involves a plurality of pretreatment units, a plurality of gathering stations, a plurality of pumps, at least one collection line and a final treatment station. The process involves preliminary treatment, or pretreatment, of the wastewater at or near the wastewater generating site, gathering the pretreated wastewater from the various waste-generating sites, transporting the pretreated wastewater to a final treatment location and providing final treatment of the wastewater to produce effluent discharge that conforms to regulatory, environmental or sound practice standards, or alternatively, to provide discharge suitable for reuse within applicable regulatory, environmental or sound practice limits.